Protecting device for electric detonators



Nav. 9, 1926. 1,606,417

Harry L. Gfaz,

I Patented Nov. 9,1926@ HARRY L. GRANT, OF `'TAMAQ''A, PENNSYLVANIA, ASSIGNOR TO ATLAS POWDER COMPANY, F WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE.

PRO'llElC'JIITG- DEVICEVFOR ELECTRIC' DETONATORS.

Application led November 20; 1925. Serial No. 70,368.

This invention relates to a protecting device for electric detonators of the character of that shown in my copending application, Serial No. 7 48,214, -filed on November 6, 1924.

Like the device of the application referred to, the protectingA4 device 'of the present invention is intended to be applied to the leadin wires of electric detonators and to Serve, while in position, to establish a short circuit 10 between the two lead-in Awires, so that any stray -currents imposed uponv the lead-in wires, outwardly of the point of application of said device, may not find their way to the detonator and prematurely explode the same and so that no difference in potential can be created between the lead wires inwardly of the point of application of the device under the influence of accidental or stray currents imposed upon said wires. Y

I am aware of the fact that it has been proposed to short circuit the main firing cable leading from the blasting machine. However, that method is of utility only at the time of use. An important object of the vpresent invention is to providea structure V'which will be operative with respect to the .individual detonators, at all times between the time of manufacture of the detonator and until the same is actually exploded pn the job.V the structure being of particular utility during the time that the detonator is being transported and while it is being handled about the work preliminary to the actual connection of its leadwires to the main firing cable.

' The present application is directedvto the protection of a specific form of short circuiting shunt and method of applying the same to the lead-in wires of the individual blasting caps with its innerlend abutting and resting rmly against the terminal end of F ig. 1 is a view of the Ablank from which the shunt is made,`

Fig, 2 is a perspective view of the 'shunt before application, and

, from the wires.

Fig. 3 is a side view of a detonator having the shunt applied thereto.

Like numerals designate corresponding parts in all of the figures of the drawing.

Referring to the drawing, 5 designates the conventional electric detonator and 6 and7 designate the usual lead-in wires of said detonator. 'l

In' the ordinary use of the detonator thev flow of current of sufficient strength past an igniting element 8, which connects the inner ends of the wires 6 and 7 explodes the detonator, The lead-in wires are insulated, as indicated at 9 and 10', for some distance from the detonator and the ends of the lead-in wiresv are left bare beyond the point where the insulation terminates, to adapt them for ready application to the tiring cable, leading from a blasting machine.

" The shunt of the present invention comprises a metal strip 11, which is notched from its opposite edges as indicated at 12v is manifest that the interlocking of the lead wires in these notches, cut from opposite directions, renders the accidental dislodgement of the shimt from the lead wires, practically impossible. Furthermore, this arrangement aids in maintaining the shunt inv position upon the wires during thecclamping operation. When lit is desired to remove the shunt, preparatory to use of the detonator, the shunt may be stripped longitudinally the shunt from the wires aids in cleaning them and, to increase the cleaning and scraping action of the shunt upon the wlres, the

`edges of the slots 12 and 13 are madel as sharp as possible. The result is that the wires are rendered bright and clean and put 1n such condition asto make effective elec- This action of stripping -trical union with the mainA blasting cable when they are attached thereto. By referv'ring to Fig. 3, it will be seenthat the-shunt is positioned so 4that it closely abuts the terminal ends of the insulation uponv the lead wires. Since this insulating material proy tects the lead Wires from the shunt, inwardly, and the shunt itself protects the detonator vfrom the point of its application, outwardly, it is clear that as long as the shunt remains in position, the detonator cannot possibly be exploded by stray currents from any source whatever, because no difference in potential can be created between the lead Wires inwardly of the shunt. It is not to be understood that thedevice is of utility only when actually touching the termination of the insulation. It will give a very appreciable measure of protection even when spaced somewhat from the insulation becauser the infiuences which might bring about such difference in potential between thel lead wiresas to explode the detonator, are not those sought to be created by an intelligent human agency but only those which mightV accidentally occur. yStray currents of such low E. M. F. as to escape ordinary notice constitute a marked source of danger and are rendered absolutely harmless by this invention. y

It is to be understood that the invention is not limited to the precise construction set forth but that it includes within its purview whatever changes fairly come within either the terms or the spirit of the appended claims. Y

Having described my invention, what I claim is:

1. The herein described method of applyf ing a shunt to an electric detonator, which consists of notching. strip of conductive material in opposite directions from its op,- posite edges, bending said material upon itself to bring said notches into substantial alignment, passing the bared portions of the lead Wires'through said notches and com-` ing a shunt to an electric detonator, which consists of notching a piece of conductive material from its opposite edges, bending said conductive material upon itself, inserting the lead wires ofthe detonator in said notched vportions and then clamping the shunt into firm engagement with said wires by forcing the bent portions of said strip toward each other.

3. A shunt of the character described comprising a flat strip of conductive material notched from its opposite edges and bent upon itself, to bring its notched portions into alignment with each other 'in such manner that Wires to be united may be threaded through said notched portions.

4. A shunt of the character described comprising a piece of fiat sheet metal notched from its opposite edges, bent upon itself and compressed into firm engagement with the lead Wires of a detonator, which lead wires pass through said notched portions.

The combination with an electric detonator, the lead wires of which are covered with insulating material for a portion of their lengt-l1 and are bare for the remainder of their length, of a shunt comprising a flat piece of metal slotted from its opposite edges vand bent upon itself, said wires passing through said slotted portions and the material of the shunt being forcibly pressed into engagement with said wires, by bending its free'e'nds toward each other.

I In testimony whereof ture.

HARRY L. GRANT.

he attixes his signa- 

